An X-ray device refers to, e.g., a device that diagnoses the health condition of a human patient or an animal by transmitting a beam of X-rays through an object such as the human patient or the animal and acquiring an X-ray image from the beam of X-rays coming out of the object.
Shown in FIG. 1 is a conventional portable X-ray device. Referring to d1, an X-ray device 10 is designed to generate a beam of X-rays and irradiate it on an image capturing unit 20. As the image capturing unit 20, use is made of a digital imaging panel that can capture an X-ray image using an X-ray film or a multiplicity of photo sensors.
An object 30 whose X-ray image is to be captured is positioned between the X-ray device 10 and the image capturing unit 20. The beam of X-rays irradiated from the X-ray device 10 pass through the object 30. Using the beam of X-rays transmitted through the object 30, the image capturing unit 20 captures an X-ray image of the object 30.
In order to obtain an accurate X-ray image of the object 30, there is a need to identify an X-ray irradiation region on the object 30 prior to taking the X-ray image of the object 30. Since the beam of X-rays is not visually recognizable, it is necessary to use an additional unit that enables a user to visually identify the X-ray irradiation region. The unit that enables a user to visually identify and adjust the X-ray irradiation region is typically referred to as a collimator. The collimator serves to direct the light of a lamp toward the X-ray irradiation region, thereby enabling the user to identify the X-ray irradiation region through the lamp light.
FIG. 2 shows an exemplary use of the conventional X-ray device 10 that indicates an X-ray irradiation region with a typical lamp. Referring to FIG. 2, a collimator for indicating an X-ray irradiation region with a lamp is provided within the X-ray device 10. In order to take an X-ray image of an object, the collimator illuminates the light of a lamp on an image capturing unit 20. The light thus illuminated divides the image capturing unit 20 into an illumination region 35 and a non-illumination region 37. The illumination region 35 of the image capturing unit 20 is equivalent to an actual X-ray irradiation region. Based on the illumination region 35, the user can identify the actual X-ray irradiation region and can accurately take an X-ray image of a target portion of an object by positioning the target portion in the illumination region 35.
FIG. 3 schematically depicts the internal construction of the conventional X-ray device in which an X-ray irradiation region is indicated with a typical lamp. Referring to FIG. 3, a reflection mirror 15 having a specified inclination relative to an X-ray irradiation axis 12 is arranged between an X-ray tube 11 that generates and irradiates a beam of X-rays on an object and a shutter 17 and 18 that regulates the irradiation area of the beam of X-rays. A lamp 13 is arranged below the reflection mirror 15 so that the light emitted from the lamp 13 can be illuminated on the reflection mirror 15. Then, the light is reflected by the reflection mirror 15 to move along the X-ray irradiation axis 12. The illumination area of the light moving along the X-ray irradiation axis 12 is regulated by the shutter 17 and 18, after which the light is illuminated on an image capturing unit. The illumination area of the light on the image capturing unit is the same as the X-ray irradiation region over which the beam of X-rays are actually irradiated by the x-ray tube 11. The user can identify the X-ray irradiation region by observing the illumination region of the light illuminated on the image capturing unit.
For the purpose of simplicity in description, FIG. 3 shows only an upper shutter blade 17 for regulating an upper edge of the beam of X-rays irradiated on the object and a lower shutter blade 18 for regulating a lower edge of the beam of X-rays. It should be noted, however, that the X-ray device further includes a left shutter blade for regulating a left edge of the beam of X-rays and a right shutter blade for regulating a right edge of the beam of X-rays.
With the conventional X-ray device stated above, the lamp has to be arranged between the X-ray tube and the shutter in order for the user to identify the X-ray irradiation region. This makes it necessary to provide a lamp-receiving space between the X-ray tube and the shutter. It is also necessary to provide a space and a vent hole for dissipating the heat generated from the lamp. For that reason, the conventional X-ray device is doomed to be fabricated with a greater size and an increased weight. Furthermore, the conventional X-ray device has a problem in that a large amount of electric power is consumed in operating the lamp.
The size of the shutter required to regulate the irradiation area of the beam of X-rays becomes greater as the shutter is positioned farther away from the focal point of the X-ray tube. Typically, the shutter is made of heavy and X-ray impermeable lead that can effectively regulate the irradiation area of the beam of X-rays irradiated on the object. This means that the size and weight of the X-ray device is increased in proportion to the size of the shutter. In case of the conventional X-ray device mentioned above, the distance between the X-ray tube and the focal point must be greater than a specified value to accommodate the lamp and the reflection mirror. This poses a problem in that the conventional X-ray device is constrained to use a shutter having a greater size and an increased weight.